22 results on '"Houzeaux, Guillaume"'
Search Results
2. A Chimera method based on a Dirichlet/Neumann(Robin) coupling for the Navier–Stokes equations
- Author
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Houzeaux, Guillaume and Codina, Ramon
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FLOWS (Differentiable dynamical systems) , *FINITE element method , *COUPLINGS (Gearing) - Abstract
We present a Chimera method for the numerical solution of incompressible flows past objects in relative motion. The Chimera method is implemented as an iteration-by-subdomain method based on Dirichlet/Neumann(Robin) coupling. The DD method we propose is not only geometric but also algorithmic, for the solution on each subdomain is obtained on separate processes and the exchange of information between the subdomains is carried out by a master code. This strategy is very flexible as it requires almost no modification to the original numerical code. Therefore, only the master code has to be adapted to the numerical codes and the strategies used on each subdomain. As a basic flow solver, we a use stabilized finite element method. [Copyright &y& Elsevier]
- Published
- 2003
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3. Parallel uniform mesh multiplication applied to a Navier–Stokes solver.
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Houzeaux, Guillaume, de la Cruz, Raúl, Owen, Herbert, and Vázquez, Mariano
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PARALLEL computers , *MULTIPLICATION , *NAVIER-Stokes equations , *SIMULATION methods & models , *APPROXIMATION theory , *HIGH performance computing , *SUPERCOMPUTERS - Abstract
Abstract: We present here the enhancement of a parallel incompressible Navier–Stokes solver to be able to manage very large meshes. Mesh generation in engineering applications is often the bottleneck of the complete simulation process. The mesh is the basis of the discretization algorithm and the first “lego” of a simulation. A mesh should approximate well the necessary geometrical elements of the computational domain. In addition, it should be fine enough to capture the relevant physical scales of the engineering problem. Usually, commercial mesh generators do well with the first task. They include refinement tools for boundary layer elements and local adaptivity. However, it is quite difficult to generate very large meshes (say of the order of thousands of millions of elements) with the available tools. The idea of this work is to implement a parallel uniform mesh multiplication in a HPC code developed at Barcelona Supercomputing Center named Alya. [Copyright &y& Elsevier]
- Published
- 2013
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4. A parallel coupling strategy for the Chimera and domain decomposition methods in computational mechanics.
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Eguzkitza, Beatriz, Houzeaux, Guillaume, Aubry, Romain, Owen, Herbert, and Vázquez, Mariano
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MATHEMATICAL decomposition , *COMPUTATIONAL mechanics , *APPROXIMATION theory , *BOUNDARY value problems , *NAVIER-Stokes equations , *STOCHASTIC convergence - Abstract
Abstract: Domain Decomposition Methods (DDMs) are techniques that divide the solution of a PDE on a domain into smaller solutions on smaller subdomains coupling them using a certain strategy. They are used for essentially two purposes: designing parallel solvers and/or coupling subdomains with different meshes, different numerical approximations, etc. In this paper we are interested in this last category. One example of application is the Chimera method. In that sense, the Chimera method can be viewed as a preprocess technique plus a DDM on overlapping and non-conforming subdomains. The coupling technique of DDM is usually achieved via transmission conditions to impose the continuities of the unknown and its flux across the subdomain boundaries. We propose in this work an alternative coupling strategy, intervening as a preprocess method. It consists in connecting the nodes of one subdomain with the nodes of the adjacent subdomains via newly created elements. In this way, the multi-domain character of a DDM disappears, making it a parallel, implicit and versatile method. We discuss in this paper the relation between the proposed method and the existing coupling strategies. We also present some convergence results as well as some applications to the Navier–Stokes equations and other PDE’s. [Copyright &y& Elsevier]
- Published
- 2013
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5. A finite element method for the solution of rotary pumps
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Houzeaux, Guillaume and Codina, Ramon
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NUMERALS , *MATHEMATICS , *MILITARY strategy , *SIMULATION methods & models , *METHODOLOGY , *PUMPING machinery , *GEARING machinery , *MACHINERY - Abstract
We present in this paper a numerical strategy for the simulation of rotary positive displacement pumps, taking as an example a gear pump. While the two gears of the pump are rotating, the intersection between them changes in time. Therefore, the computational domain should be recomputed in some way at each time step. The strategy used here consists in dividing a cycle into a certain number of time steps and obtaining different computational meshes for each of these time steps. The coupling between two consecutive time steps is achieved by interpolating the flow unknowns in a proper way. This geometrical decomposition enables one to have a plain control over the mesh, particularly in the zones of interest, which are the gap between the gears and the casing, and the engagement and disengagement zones of the gears. [Copyright &y& Elsevier]
- Published
- 2007
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6. Forest density is more effective than tree rigidity at reducing the onshore energy flux of tsunamis.
- Author
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Mukherjee, Abhishek, Cajas, Juan Carlos, Houzeaux, Guillaume, Lehmkuhl, Oriol, Suckale, Jenny, and Marras, Simone
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FOREST density , *COMPUTATIONAL fluid dynamics , *FLUID-structure interaction , *COASTAL forests , *TSUNAMIS , *TREE trunks , *HARDWOODS - Abstract
Communities around the world are increasingly interested in nature-based solutions to the mitigation of coastal risks by coastal forests, but it remains unclear how much protective benefits vegetation provides, particularly in the limit of highly energetic flows after tsunami impact. The current study, using a three-dimensional incompressible computational fluid dynamics model with a fluid–structure interaction approach, aims to quantify how energy reflection and dissipation vary with different degrees of rigidity and vegetation density of a coastal forest. We represent tree trunks as cylinders and use the elastic modulus of hardwood trees such as pine or oak to characterize the rigidity of these cylinders. The numerical results show that energy reflection increases with rigidity only for a single cylinder. In the presence of multiple cylinders, the difference in energy reflection created by varying rigidity diminishes as the number of cylinders increases. Instead of rigidity, we find that the blockage area created by the presence of multiple tree trunks dominates energy reflection. As tree trunks are deformed by the hydrodynamic forces, they alter the flow field around them, causing turbulent kinetic energy generation in the wake region. As a consequence, trees dissipate flow energy, highlighting coastal forests reducing the onshore energy flux of tsunamis by means of both reflection and dissipation. • The number of tree trunks and the spacing between them are more important for tsunami-risk mitigation than the species-specific properties. • Deflection of tree trunks alters the flow field around them, causing turbulent kinetic energy generation in the wake region. • Coastal forests reduces the onshore energy flux of tsunamis by means of both reflection and dissipation. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Ventricular anatomical complexity and sex differences impact predictions from electrophysiological computational models.
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Gonzalez-Martin, Pablo, Sacco, Federica, Butakoff, Constantine, Doste, Ruben, Bederian, Carlos, Gutierrez Espinosa de los Monteros, Lilian K., Houzeaux, Guillaume, Iaizzo, Paul A., Iles, Tinen L., Vazquez, Mariano, and Aguado-Sierra, Jazmin
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ELECTROPHYSIOLOGY , *VENTRICULAR tachycardia , *HEART size , *CARDIAC pacing , *MYOCARDIAL infarction , *FINITE element method , *ARRHYTHMIA - Abstract
The aim of this work was to analyze the influence of sex hormones and anatomical details (trabeculations and false tendons) on the electrophysiology of healthy human hearts. Additionally, sex- and anatomy-dependent effects of ventricular tachycardia (VT) inducibility are presented. To this end, four anatomically normal, human, biventricular geometries (two male, two female), with identifiable trabeculations, were obtained from high-resolution, ex-vivo MRI and represented by detailed and smoothed geometrical models (with and without the trabeculations). Additionally one model was augmented by a scar. The electrophysiology finite element model (FEM) simulations were carried out, using O'Hara-Rudy human myocyte model with sex phenotypes of Yang and Clancy. A systematic comparison between detailed vs smooth anatomies, male vs female normal hearts was carried out. The heart with a myocardial infarction was subjected to a programmed stimulus protocol to identify the effects of sex and anatomical detail on ventricular tachycardia inducibility. All female hearts presented QT-interval prolongation however the prolongation interval in comparison to the male phenotypes was anatomy-dependent and was not correlated to the size of the heart. Detailed geometries showed QRS fractionation and increased T-wave magnitude in comparison to the corresponding smoothed geometries. A variety of sustained VTs were obtained in the detailed and smoothed male geometries at different pacing locations, which provide evidence of the geometry-dependent differences regarding the prediction of the locations of reentry channels. In the female phenotype, sustained VTs were induced in both detailed and smooth geometries with RV apex pacing, however no consistent reentry channels were identified. Anatomical and physiological cardiac features play an important role defining risk in cardiac disease. These are often excluded from cardiac electrophysiology simulations. The assumption that the cardiac endocardium is smooth may produce inaccurate predictions towards the location of reentry channels in in-silico tachycardia inducibility studies. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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8. A Level Set-Based Actuator Disc Model for Turbine Realignment in Wind Farm Simulation: Meshing, Convergence and Applications.
- Author
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Gargallo-Peiró, Abel, Revilla, Gonzalo, Avila, Matias, and Houzeaux, Guillaume
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WIND turbines , *WIND power plants , *ACTUATORS , *SET functions , *TURBINES - Abstract
We present a novel meshing and simulation approach for wind farms, featuring realignment and mesh adaptation. The turbines are modeled with actuator discs, which are discretized by means of an adaptation process to represent a level set function. The level-set-based simulation framework is combined with an adaptation cycle to capture both the solution and the actuator discs. In addition, we devise a turbine realignment process which takes into account the actual flow in the actuator disc configuration. Several results are presented to highlight the features of the approach. First, the adaptive simulation approach is validated, fulfilling the theoretical convergence rates and improving the accuracy of the boundary tight representations. Second, the adaptive simulation process is applied to a full wind farm configuration featuring 219 turbines, illustrating that is it well devised for complex wind farm configurations. Third, the turbine reorientation process is validated in a one turbine scenario. Finally, the realignment simulation framework is applied in a wind farm featuring 115 turbines. The presented results outline the significance of the proposed work, enabling turbine realignment and mesh adaptation to perform accurate simulations of complex wind farm configurations. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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9. Local preconditioning and variational multiscale stabilization for Euler compressible steady flow.
- Author
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Moragues Ginard, Margarida, Vázquez, Mariano, and Houzeaux, Guillaume
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STABILITY (Mechanics) , *EULER equations , *STEADY-state flow , *COMPRESSIBLE flow , *FINITE element method , *STIFFNESS (Mechanics) , *MACH number - Abstract
This paper introduces a preconditioned variational multiscale stabilization (P-VMS) method for compressible flows. In this introductory paper we focus on inviscid flow and steady state problems. The Euler equations are solved on fully unstructured grids and discretized using the finite element method. The P-VMS method can be decomposed into three parts. First, a local preconditioner is applied to the continuous equations to reduce the stiffness while covering a wide range of Mach numbers. Then, the resulting preconditioned system is discretized in space using finite elements and stabilized with a variational multiscale stabilization method adapted for the preconditioned equations. In this paper, the solution is advanced in time using a fully explicit time discretization, although P-VMS is general and can be applied to fully implicit solvers. The proposed method is assessed by comparing convergence and accuracy of the solutions between the non-preconditioned and preconditioned cases, in particular for van Leer–Lee–Roe ’s (1991) and Choi-Merkle ’s (1993) preconditioners, in some selected examples covering a large range of Mach numbers. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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10. Validations of the radiation transport module NEUTRO: A deterministic solver for the neutron transport equation.
- Author
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Soba, Alejandro, Cazado, Mauricio E., Houzeaux, Guillaume, Gutierrez-Milla, Albert, Mantsinen, Mervi J., and Saez, Xavier
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NEUTRON transport theory , *TRANSPORT equation , *BOLTZMANN'S equation , *RADIATION , *NEUTRONS , *SPHERICAL harmonics - Abstract
• A radiation transport solver describing neutronic transport is introduced. • The model is used to reproduce shielding benchmarks included in SINBAD database. • The solver is included as a module into the high-performance computational mechanics code ALYA. • The results obtained achieved good accuracy over extended domains. • This implementation in Alya will allow coupling of radiation transport with thermo-mechanical solutions in large domains. We present significant improvements and validations of a deterministic neutron transport code (NEUTRO) dedicated to solving the Boltzmann Transport Equation. The code is integrated as a module in the Alya software package developed by the Barcelona Supercomputing Center which uses the Discrete Ordinates Method on angular coordinates, multi-group for energy discretization and FEM on unstructured meshes to treat special complex domains. The anisotropy of the scattering medium is introduced into the scattering kernel using real base expressions for spherical harmonics. In order to build the total cross-section and the respective group matrix for the elastic cross-section, we use the NJOY code. We test the solver using different geometries, orders of integration for the angular discretization and number of energy groups. Finally, we compare our results against benchmarks obtained from an NEA database that reported measurements of leakage spectra of several materials. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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11. A portable coding strategy to exploit vectorization on combustion simulations.
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Banchelli, Fabio, Oyarzun, Guillermo, Garcia-Gasulla, Marta, Mantovani, Filippo, Both, Ambrus, Houzeaux, Guillaume, and Mira, Daniel
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COMBUSTION , *BLOCK codes , *COMPILERS (Computer programs) , *DATA structures , *CYCLING instruction , *HIGH performance computing - Abstract
The complexity of combustion simulations demands the latest high-performance computing tools to accelerate its time-to-solution results. A current trend on HPC systems is the utilization of CPUs with SIMD or vector extensions to exploit data parallelism. Our work proposes a strategy to improve the automatic vectorization of finite-element-based scientific codes. The approach applies a parametric configuration to the data structures to help the compiler detect the block of codes that can take advantage of vector computation while maintaining the code portable. A detailed analysis of the computational impact of this methodology on the different stages of a CFD solver is studied on the PRECCINSTA burner simulation. Our parametric implementation has proven to help the compiler generate more vector instructions in the assembly operation: this results in a reduction of up to 9. 39 × of the total executed instruction maintaining constant the Instructions Per Cycle and the CPU frequency. The proposed strategy improves the performance of the CFD case under study up to 4. 67 × on the MareNostrum 4 supercomputer. • A parametric configuration of the CFD data structures is presented for enabling auto-vectorization. • A detailed performance analysis using different compilers is applied to a real CFD case. • A reduction of up to 9.39 times of the total executed instruction is attained, maintaining constant the IPC and the CPU frequency. • The proposed strategy accelerates up to 4.67 the PRECCINSTA burner simulation on the Marenostrum4 nodes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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12. Nasal sprayed particle deposition in a human nasal cavity under different inhalation conditions.
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Calmet, Hadrien, Inthavong, Kiao, Eguzkitza, Beatriz, Lehmkuhl, Oriol, Houzeaux, Guillaume, and Vázquez, Mariano
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NASAL cavity , *LOGNORMAL distribution , *INTRANASAL medication , *PARTICLE size distribution , *PARTICLES , *PHYSICAL & theoretical chemistry - Abstract
Deposition of polydisperse particles representing nasal spray application in a human nasal cavity was performed under transient breathing profiles of sniffing, constant flow, and breath hold. The LES turbulence model was used to describe the fluid phase. Particles were introduced into the flow field with initial spray conditions, including spray cone angle, insertion angle, and initial velocity. Since nasal spray atomizer design determines the particle conditions, fifteen particle size distributions were used, each defined by a log-normal distribution with a different volume mean diameter (Dv50). Particle deposition in the anterior region was approximately 80% when Dv50 > 50μm, and this decreased to 45% as Dv50 decreased to 10μ m for constant and sniff breathing conditions. The decrease in anterior deposition was countered with increased deposition in the middle and posterior regions. The significance of increased deposition in the middle region for drug delivery shows there is potential for nasal delivered drugs to reach the highly vascularised mucosal walls in the main nasal passages. For multiple targeted deposition sites, an optimisation equation was introduced where deposition results of any two targeted sites could be combined and a weighting between 0 to 1 was applied to each targeted site, representing the relative importance of each deposition site. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. New high performance computing software for multiphysics simulations of fusion reactors.
- Author
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Gutierrez-Milla, Albert, Mantsinen, Mervi, Avila, Matias, Houzeaux, Guillaume, Riera-Auge, Carles, and Sáez, Xavier
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FUSION reactors , *TOKAMAKS , *NEUTRON transport theory , *PLASMA physics , *SIMULATION methods & models - Abstract
Highlights • Presentation of Alya computational mechanics code in the fusion field. • Including a neutronics module within an HPC multiphysics framework. • First benchmark results of the neutron transport module. Abstract Integrated modelling is an important element of tokamak fusion research. It contributes to the interpretation and planning of experiments, validation of theory against experimental results, development of plasma control techniques as well as the design of next step devices. Large efforts continue to be devoted to the integrated modelling of plasma physics effects in a fusion reactor core and have led to significant progress in physics understanding, while tools to model multiphysics phenomena taking place in fusion reactor components such as tritium breeding blankets have not yet reached a similar level of detail and completeness. We are developing a new high performance computing tool for simulating the latter effects. It is based a parallel computational mechanics code Alya which is specially designed for running with high efficiency standards in large scale supercomputers and is capable of solving different physics problems in a coupled way. As first step towards multiphysics simulations of fusion reactor components, we are developing a new neutron transport module based on the deterministic approach for coupling with the existing, implemented physics modules in Alya. This module, together with existing physics implemented in Alya will allow to solve future high fidelity multiphysics and multiscale problems. We present the capabilities of the Alya system and the latest version of the new neutron transport module currently under development. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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14. Fluid–structure interaction of human nasal valves under sniff conditions and transport of inhaled aerosols: A numerical study.
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Calmet, Hadrien, Santiago, Alfonso, Cajas, Juan Carlos, Langdon, Cristobal, Eguzkitza, Beatriz, and Houzeaux, Guillaume
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FLUID-structure interaction , *COMPUTATIONAL fluid dynamics , *SOCIAL interaction , *VALVES , *AEROSOLS - Abstract
The nasal valve is the narrowest part of the nasal airway which is responsible for the largest part of the nasal resistance. Even little changes in the aperture can affect the flow downstream through the nose significantly. Its principal function is to limit airflow for example during a rapid and short inhalation, also called a sniff. Coupling Computational Fluid Dynamics (CFD) with Fluid–Structure Interaction (FSI) allows solving and exchanging force and displacement between the solid and fluid domains and offers a more accurate representation of the physical system in confined flow cases. Furthermore, particle transport and deposition are performed in this study to reveal the effect of the complex coupling on the nasal cavity deposition of inhaled aerosols. Two different configurations are used to model the nasal valve and differences in magnitudes in deformations are observed during the sniff. A comparison between FSI results and the in-vivo evaluation of the deformation shows an acceptable agreement as to the first step of validation. In addition, the results demonstrated that FSI increases significantly the particle deposition in the nasal cavity and the micro-particle diameter is the critical range parameter to enhance deposition with nasal valve deformation during a sniff. • The results demonstrated that FSI increases significantly the particle deposition in the nasal cavity. • The micro-particle diameter is the critical range parameter to enhance deposition with nasal valve deformation during a sniff. • The Comparison between FSI results and the in-vivo evaluation of the deformation shows an acceptable agreement as first step of validation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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15. Fourier stability analysis and local Courant number of the preconditioned variational multiscale stabilization (P-VMS) for Euler compressible flow.
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Moragues Ginard, Margarida, Bernardino, Gabriel, Vázquez, Mariano, and Houzeaux, Guillaume
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FOURIER analysis , *NUMBER theory , *COMPRESSIBLE flow , *EULER equations (Rigid dynamics) , *MACH number - Abstract
The results of a Fourier stability analysis of the preconditioned variational multiscale stabilization (P-VMS) method introduced in Moragues et al. (2015) are presented in this paper. P-VMS combines a variational multiscale stabilized finite elements discretization together with local preconditioning. In this work, we deal with the P-VMS method using van Leer–Lee–Roe ’s (vanLeer et al., 1991) and Choi–Merkle ’s (Choi and Merkle, 1993) local preconditioners. We solve the Euler equations of compressible flow for steady problems. We concentrate on explicit time integration schemes. The stability analysis is performed on a two dimensional simplified problem with a structured mesh and its conclusions are applied to two and three dimensional general problems with unstructured meshes. As a result of this analysis a local Courant–Friedrichs–Lewy number is defined for the computation of the time step. The convergence rate is evaluated, and compared with the traditional constant Courant–Friedrichs–Lewy number for various test cases spanning a large range of Mach numbers. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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16. Broadcast-Enabled Massive Multicore Architectures: A Wireless RF Approach.
- Author
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Abadal, Sergi, Sheinman, Benny, Katz, Oded, Markish, Ofer, Elad, Danny, Fournier, Yvan, Roca, Damian, Hanzich, Mauricio, Houzeaux, Guillaume, Nemirovsky, Mario, Alarcon, Eduard, and Cabellos-Aparicio, Albert
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MULTICORE processors , *RADIO frequency , *COMPUTER architecture , *MULTIPROCESSORS , *COMPUTER algorithms - Abstract
Broadcast traditionally has been regarded as a prohibitive communication transaction in multiprocessor environments. Nowadays, such a constraint largely drives the design of architectures and algorithms all-pervasive in diverse computing domains, directly and indirectly leading to diminishing performance returns as the many-core era is approaching. Novel interconnect technologies could help revert this trend by offering, among others, improved broadcast support, even in large-scale chip multiprocessors. This article outlines the prospects of wireless on-chip communication technologies pointing toward low-latency (a few cycles) and energy-efficient broadcast (a few picojoules per bit). It also discusses the challenges and potential impact of adopting these technologies as key enablers of unconventional hardware architectures and algorithmic approaches, in the pathway of significantly improving the performance, energy efficiency, scalability, and programmability of many-core chips. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
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17. Dynamic load balance of chemical source term evaluation in high-fidelity combustion simulations.
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Ramirez-Miranda, Guillem, Mira, Daniel, Pérez-Sánchez, Eduardo J., Surapaneni, Anurag, Borrell, Ricard, Houzeaux, Guillaume, and Garcia-Gasulla, Marta
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DYNAMIC balance (Mechanics) , *CHEMICAL kinetics , *COMBUSTION , *FLAME , *FLOW simulations , *DYNAMIC loads , *NUMERICAL integration - Abstract
This paper presents a load balancing strategy for reaction rate evaluation and chemistry integration in reacting flow simulations. The large disparity in scales during combustion introduces stiffness in the numerical integration of the PDEs and generates load imbalance during the parallel execution. The strategy is based on the use of the DLB library to redistribute the computing resources at node level, lending additional CPU-cores to higher loaded MPI processes. This approach does not require explicit data transfer and is activated automatically at runtime. Two chemistry descriptions, detailed and reduced, are evaluated on two different configurations: laminar counterflow flame and a turbulent swirl-stabilized flame. For single-node calculations, speedups of 2.3x and 7x are obtained for the detailed and reduced chemistry, respectively. Results on multi-node runs also show that DLB improves the performance of the pure-MPI code similar to single node runs. It is shown DLB can get performance improvements in both detailed and reduced chemistry calculations. • A load balancing strategy for reaction rate and chemistry integration is presented. • It uses the DLB library to redistribute the computational resources at node level. • Code hybridization improves the performance over MPI-pure implementations. • Single-node and multi-node tests show speedups in reacting flow calculations. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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18. An XFEM/CZM implementation for massively parallel simulations of composites fracture.
- Author
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Vigueras, Guillermo, Sket, Federico, Samaniego, Cristóbal, Wu, Ling, Noels, Ludovic, Tjahjanto, Denny, Casoni, Eva, Houzeaux, Guillaume, Makradi, Ahmed, Molina-Aldareguia, Jon M., Vázquez, Mariano, and Jérusalem, Antoine
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COMPOSITE materials , *FRACTURE mechanics , *SURFACE cracks , *FINITE element method , *MECHANICAL behavior of materials , *STRENGTH of materials - Abstract
Because of their widely generalized use in many industries, composites are the subject of many research campaigns. More particularly, the development of both accurate and flexible numerical models able to capture their intrinsically multiscale modes of failure is still a challenge. The standard finite element method typically requires intensive remeshing to adequately capture the geometry of the cracks and high accuracy is thus often sacrificed in favor of scalability, and vice versa. In an effort to preserve both properties, we present here an extended finite element method (XFEM) for large scale composite fracture simulations. In this formulation, the standard FEM formulation is partially enriched by use of shifted Heaviside functions with special attention paid to the scalability of the scheme. This enrichment technique offers several benefits since the interpolation property of the standard shape function still holds at the nodes. Those benefits include (i) no extra boundary condition for the enrichment degree of freedom, and (ii) no need for transition/blending regions; both of which contribute to maintaining the scalability of the code. Two different cohesive zone models (CZM) are then adopted to capture the physics of the crack propagation mechanisms. At the intralaminar level, an extrinsic CZM embedded in the XFEM formulation is used. At the interlaminar level, an intrinsic CZM is adopted for predicting the failure. The overall framework is implemented in ALYA, a mechanics code specifically developed for large scale, massively parallel simulations of coupled multi-physics problems. The implementation of both intrinsic and extrinsic CZM models within the code is such that it conserves the extremely efficient scalability of ALYA while providing accurate physical simulations of computationally expensive phenomena. The strong scalability provided by the proposed implementation is demonstrated. The model is ultimately validated against a full experimental campaign of loading tests and X-ray tomography analyzes. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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19. Algebraic multigrid preconditioning within parallel finite-element solvers for 3-D electromagnetic modelling problems in geophysics.
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Koldan, Jelena, Puzyrev, Vladimir, de la Puente, Josep, Houzeaux, Guillaume, and Cela, José María
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ELECTROMAGNETIC fields , *GEOPHYSICAL prospecting , *ALGEBRAIC multigrid methods , *ITERATIVE methods (Mathematics) , *MATHEMATICAL models , *FINITE element method - Abstract
We present an elaborate preconditioning scheme for Krylov subspace methods which has been developed to improve the performance and reduce the execution time of parallel node-based finite-element (FE) solvers for 3-D electromagnetic (EM) numerical modelling in exploration geophysics. This new preconditioner is based on algebraic multigrid (AMG) that uses different basic relaxation methods, such as Jacobi, symmetric successive over-relaxation (SSOR) and Gauss–Seidel, as smoothers and the wave front algorithm to create groups, which are used for a coarse-level generation. We have implemented and tested this new preconditioner within our parallel nodal FE solver for 3-D forward problems in EM induction geophysics. We have performed series of experiments for several models with different conductivity structures and characteristics to test the performance of our AMG preconditioning technique when combined with biconjugate gradient stabilized method. The results have shown that, the more challenging the problem is in terms of conductivity contrasts, ratio between the sizes of grid elements and/or frequency, the more benefit is obtained by using this preconditioner. Compared to other preconditioning schemes, such as diagonal, SSOR and truncated approximate inverse, the AMG preconditioner greatly improves the convergence of the iterative solver for all tested models. Also, when it comes to cases in which other preconditioners succeed to converge to a desired precision, AMG is able to considerably reduce the total execution time of the forward-problem code—up to an order of magnitude. Furthermore, the tests have confirmed that our AMG scheme ensures grid-independent rate of convergence, as well as improvement in convergence regardless of how big local mesh refinements are. In addition, AMG is designed to be a black-box preconditioner, which makes it easy to use and combine with different iterative methods. Finally, it has proved to be very practical and efficient in the parallel context. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
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20. Computational modelling of an aerosol extraction device for use in COVID-19 surgical tracheotomy.
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Calmet, Hadrien, Bertomeu, Pablo Ferrer, McIntyre, Charlotte, Rennie, Catherine, Gouder, Kevin, Houzeaux, Guillaume, Fletcher, Christian, Still, Robert, and Doorly, Denis
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COVID-19 , *MICROBIOLOGICAL aerosols , *COVID-19 pandemic , *AEROSOLS , *COMPUTATIONAL fluid dynamics , *TRACHEOTOMY - Abstract
In view of the ongoing COVID-19 pandemic and its effects on global health, understanding and accurately modelling the propagation of human biological aerosols has become crucial. Worldwide, health professionals have been one of the most affected demographics, representing approximately 20% of all cases in Spain, 10% in Italy and 4% in China and US. Methods to contain and remove potentially infected aerosols during Aerosol Generating Procedures (AGPs) near source offer advantages in reducing the contamination of protective clothing and the surrounding theatre equipment and space. In this work we describe the application of computational fluid dynamics in assessing the performance of a prototype extraction hood as a means to contain a high speed aerosol jet. Whilst the particular prototype device is intended to be used during tracheotomies, which are increasingly common in the wake of COVID-19, the underlying physics can be adapted to design similar machines for other AGPs. Computational modelling aspect of this study was largely carried out by Barcelona Supercomputing Center using the high performance computational mechanics code Alya. Based on the high fidelity LES coupled with Lagrangian frameworks the results demonstrate high containment efficiency of generated particles is feasible with achievable air extraction rates. • Evaluation of a new device to reduce the risk of infection during Aerosol Generating Procedures for use in COVID-19 surgical tracheotomy. • High fidelity LES coupled with Lagrangian frameworks is used as results to demonstrate the efficiency. • Accurate numerical modelling of the propagation of human biological aerosols. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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21. A parallel finite-element method for three-dimensional controlled-source electromagnetic forward modelling.
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Puzyrev, Vladimir, Koldan, Jelena, de la Puente, Josep, Houzeaux, Guillaume, Vázquez, Mariano, and Cela, José María
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ELECTROMAGNETIC theory , *FINITE element method , *ELECTROMAGNETIC fields , *APPROXIMATION theory , *MAXWELL equations - Abstract
We present a nodal finite-element method that can be used to compute in parallel highly accurate solutions for 3-D controlled-source electromagnetic forward-modelling problems in anisotropic media. Secondary coupled-potential formulation of Maxwell's equations allows to avoid the singularities introduced by the sources, while completely unstructured tetrahedral meshes and mesh refinement support an accurate representation of geological and bathymetric complexity and improve the solution accuracy. Different complex iterative solvers and an efficient pre-conditioner based on the sparse approximate inverse are used for solving the resulting large sparse linear system of equations. Results are compared with the ones of other researchers to check the accuracy of the method. We demonstrate the performance of the code in large problems with tens and even hundreds of millions of degrees of freedom. Scalability tests on massively parallel computers show that our code is highly scalable. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
22. HPC compact quasi-Newton algorithm for interface problems.
- Author
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Santiago, Alfonso, Zavala-Aké, Miguel, Borrell, Ricard, Houzeaux, Guillaume, and Vázquez, Mariano
- Subjects
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ROBUST control , *ALGORITHMS , *COMPACTING - Abstract
In this work we present a robust interface coupling algorithm called Compact Interface quasi-Newton (CIQN). It is designed for computationally intensive applications using an MPI multi-code partitioned scheme. The algorithm allows to reuse information from previous time steps, feature that has been previously proposed to accelerate convergence. Through algebraic manipulation, an efficient usage of the computational resources is achieved by: avoiding construction of dense matrices and reduce every multiplication to a matrix–vector product and reusing the computationally expensive loops. This leads to a compact version of the original quasi-Newton algorithm. Altogether with an efficient communication, in this paper we show an efficient scalability up to 4800 cores. Three examples with qualitatively different dynamics are shown to prove that the algorithm can efficiently deal with added mass instability and two-field coupled problems. We also show how reusing histories and filtering does not necessarily makes a more robust scheme and, finally, we prove the necessity of this HPC version of the algorithm. The novelty of this article lies in the HPC focused implementation of the algorithm, detailing how to fuse and combine the composing blocks to obtain an scalable MPI implementation. Such an implementation is mandatory in large scale cases, for which the contact surface cannot be stored in a single computational node, or the number of contact nodes is not negligible compared with the size of the domain. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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